From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rpi!usc!wupost!uunet!psinntp!scylla!daryl Thu Feb 20 15:21:27 EST 1992
Article 3802 of comp.ai.philosophy:
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>From: daryl@oracorp.com
Subject: Re: QM nonsense
Message-ID: <1992Feb17.170325.11489@oracorp.com>
Organization: ORA Corporation
Date: Mon, 17 Feb 1992 17:03:25 GMT
Lines: 58

Matthew P Wiener writes (in response to Stanley Friesen):

>> Perhaps not, but a recent experiment has shown that a brain is not
>> necessary for causing a wave-function colapse, just any measuring
>> instrument, even if it is never looked at (indeed even if it is not
>> producing any observable output to look at).

> I have made this correction several times, and I will continue to
> make it. The above claim is nonsense, and has been known to be
> nonsense for decades. See Wigner and von Neumann's work on
> measurement.

Let me lay out what seems to be the state of affairs for quantum
measurement:

1. The laws of quantum mechanics (the Schrodinger equation, or its
relativistic, many-particle generalization) do not predict wave
function collapse, whether by measuring instruments or any other
physical process.

2. The hypothesis that "human minds" cause the wave function to
collapse into an eigenstate is in perfect agreement with all known
experiments.

These two facts seem to support von Neumann's position that there are
two kinds of quantum processes, ordinary processes that obey the
Schrodinger equation, and observational processes that cause the
collapse of the wave function. If this "two process" solution is to be
taken too literally, then it seems either that the Schrodinger
equation is incorrect for describing the behavior of physical systems,
or that human minds are *not* physical systems.

I don't think that either position is justified. Everett, DeWitt, and
others working in the 50's developed a so-called Many-Worlds
interpretation of quantum mechanics (although that name is misleading,
in my opinion). According to this interpretation, there is just one
type of process, and that is described by the Schrodinger equation.
The appearance of type-2 processes is purely subjective. In a certain
sense, when one tries to observe a superposition of, say, a spin-up
state and a spin-down state, his mind "splits" in two pieces: a mind
observing a spin-up state, and a mind observing a spin-down state.
Each "split" of the mind is incapable of observing the other, and so
the conclusion each comes to is that it is the only one, and that the
wavefunction has mysteriously collapsed.

I find this interpretation unsatisfying, in that it posits an enormous
gap between reality and our perception of reality, but it seems to
explain most of the features of the observed world. According to this
theory, consciousness has no special power to collapse the
wavefunction, although it may seem as if it does.

Daryl McCullough
ORA Corp.
Ithaca, NY






